1. Field of the Invention
This invention generally relates to a rear sprocket assembly for a bicycle. More specifically, the present invention relates a rear sprocket assembly in which more sprockets can be mounted to a freewheel of a bicycle hub assembly than a conventional rear sprocket assembly having all of the sprockets directly contacting the freewheel.
2. Background Information
In recent years, bicycle component manufacturers have been manufacturing bicycle transmissions that have more available speeds to the rider. As the available speeds in the bicycle transmission increases, the number of sprockets installed on the rear wheel also usually increases. While sprockets can be made thinner, a minimum spacing between adjacent sprockets is required to accommodate the chain. Moreover, a rear end of a conventional bicycle frame only has a limited amount of space for mounting the wheel and a rear sprocket assembly. Thus, there is a desire to increase the number of gears without changing the dimensions of the conventional bicycle frame. Accordingly, various attempts have been made in order to increase the maximum number of sprocket that can be installed on a rear hub assembly. For example, some multiple sprocket assemblies use a spider (sprocket support), which supports a plurality of ring-shaped sprocket wheels. By using a spider, a light metal such as aluminum, etc., is generally used for the spider, while various types of steel materials are used for the sprockets to provide adequate strength. One example of a multiple sprocket assembly that uses a spider is disclosed in U.S. Pat. No. 6,039,665 (assigned to Shimano Inc.),